He is refering to the meteorite which is kept in the Kabba in Mecca, and calls it that because he subscribes to the theory that much of the Koranic presentation of God (= al illah, elided to Allah) is derived from the cult of an Arabian pagan moon god, who at least in one version of Arabian paganism seems to have been the chief of their pantheon, and title "al illah" = 'the god'.
Moslems have tried and true methods for turning such folks into very good converts. It's better to know "true facts" than "funny stories" about Islamic foibles in order to counter them.
The latest in document research reveals that the earliest Korans (pre-dot Arabic) are mostly written in Syriac-Aramaic, and are better read in that language than in any construct identified as "Classical Arabic".
The most interesting things pour out of this new translation ~ one is that the oldest part of the Koran, the supposedly divinely revealed core, is mostly a Christian document designed in Damascus to be used to convert the pagans at Mecca to Christianity.
The Meccans added the rest of the stuff over the next 180 years. This is why the Koran only "refers" to material in the Bible and New Testament, and does not contain much in the way of divine text.
No doubt they knew this in the early days, particularly during the first 300 years of their history where Moslems attended Christian mass.
All are advised to read
http://www.chiesa.espressonline.it/dettaglio.jsp?id=7025&eng=y